Wrong variable name used in output string

In Learn -> The Stream API -> Finding the Characteristics of a Stream, in the "Distinct Streams" section, the variable name in the output string is different from the variable name in the code that it refers to.

Stream<String> filtered = strings.stream().distinct().filter(s -> s.length() < 5);
IO.println("Is filteredStrings sorted? " + isDistinct.test(filtered));